MCP1650 datasheet(19/20 Pages) MICROCHIP

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LED Lighting Solutions Design Guide

LED Lighting Solutions

Voltage Output Temperature Sensors

The most basic technique employed to protect the device

from damaging over-temperature conditions is to provide

a shutdown signal to the driver circuit when a pre-defined

threshold is reached. However, this behavior can be

unacceptable in applications where continuous lighting

is required for safety or regulatory conditions. A more

advanced approach can be obtained if a microcontroller is

used to manage the lighting application providing closed

loop control of the power supplied by the driver circuit.

As the temperature approaches the threshold the current

supplied can be reduced to limit the power output.

By using a Voltage Output Temperature Sensor such as

the MCP9700 and MCP9701, placed on the LED module

close to the emitting device, it is possible to provide a

linear voltage feedback signal to a PIC microcontroller. This

solution ensures that the light source can always operate at

a power level that remains within temperature limits. Almost

any kind of software algorithm can be implemented in the

microcontroller to respond to the temperature feedback,

allowing tremendous flexibility.

MCP9700/9700A

MCP9701/9701A

123

VDD

VOUT

GND

Bottom

View

5-Pin SC-70

3-Pin TO-92

MCP9700/9701

Only

VDD

VOUT

GND

MCP9700/01 Voltage Output Temperature Sensors

Power LED Thermal Control Circuit Using

MCP9700 and MCP1650

Alternatively a PIC microcontroller can perform a direct

PWM control (on/off) of the entire LED driving circuit at low

frequency (100-120 Hz). By limiting the average

on-time of the power LED, the total power output can be

limited. This technique has the advantage of stabilizing the

application temperature while maintaining the LED driving

current constant therefore limiting the LED color shift

produced by forward current changes. The diagram below

illustrates an example of a switching DC-DC converter design

based on the MCP1650 boost regulator controlled by a 6-pin

PIC10F220 microcontroller.

Learn More

The Intelligent Power Supply Design Center

(www.microchip.com/power) features temperature sensing

solutions, including application notes and product selection

charts.

Literature on the Web

■ DG4 – Temperature Sensor Design Guide, DS21895

Boost Converter

SHDN

Vcc

GND

GP0

AN1

GP2

GP3

User Interface

Communication

PWM

Power

Control

MCP1650

PIC10F220

VOUT

VCC

GND

MCP9700

Temperature

Sensing

High Power

LED Module

Power LED Thermal Control Circuit Using MCP9700 and MCP1650

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